1. Field of the Invention
The present invention relates to a thrust reverser of a bypass turbojet-engine. More particularly, it relates to a thrust reverser comprising scoop doors and a displaceable cowling panel.
2. Description of the Related Art
A bypass turbojet-engine is fitted with a conduit at the rear of the fan to channel the so-called cold, bypass flow. The conduit consists of an inner wall enclosing the structure of the actual engine and an outer wall with an upstream portion that is contiguous with the engine casing enclosing the fan. This outer wall is able to simultaneously channel the bypass flow and the primary flow in its downstream portion, namely rearward of the exhaust of the so-called hot, primary flow as regards mixed- or confluent-flow. However, in other cases the outer wall only channels the bypass flow, namely as regards separate flow.
Furthermore, a wall may fair the outside of the casing enclosing the fan and the outside of the above described conduit for the purpose of minimizing the powerplant drag. This is especially the case with powerplants projecting from the aircraft outside, in particular when these powerplants are affixed under the wings or to the rear of the fuselage.
European patent document 0,822,327 describes an illustrative embodiment, shown in FIG. 1 of the attached drawings, of a scoop-door thrustreverser of a bypass turbojet-engine.
The thrust reverser has a movable assembly and a stationary structure. The movable assembly is composed of hollow doors 3 constituting a movable portion 2 which in the forward-thrust mode form part of the external cowling. The stationary structure is composed of an upstream portion 6 upstream of the doors, a downstream portion 7 downstream of the doors 3, and beams linking the upstream portion 6 to the downstream portion 7. The stationary structure is also part of the external cowling.
The doors 3 are mounted along a circumference of the external cowling and are pivotable, in a downstream zone of their side walls, on the beams situated on each side of the doors connecting the downstream portion 7 to the upstream portion 6. The side walls link the outer structures 4 of the doors 3, which constitute part of the external cowling in the forward-thrust mode, to the inner parts 5 of the doors 3, which constitute part of the outer conduit wall.
The stationary structure's upstream portion 6 comprises a fore frame 8 which may act as a support for the displacement control system of the doors 3, for example, linear actuators. This displacement control system for the doors 3 may just as well be situated elsewhere on the periphery of the door 3, for instance downstream of it. In such a case, it will be the stationary structure's downstream portion 7 that supports the control system.
When driven into an open position, the doors 3 pivot in such a manner that the part of the door upstream of the door pivot 9 more or less obstructs the duct totally while the external structure 4 clears a passage in the external cowling to allow channeling of the bypass flow 13 and 14 radially outward relative to the longitudinal axis of the conduit: on one hand through an inner conduit 10 formed by the structure of the door 3 and on the other hand between the deflecting edge and the outside of the outer structure 4 of the door 3. The downstream part of the doors is moved into the vicinity of the outside of the external cowling. The pivoted angle is adjusted to strongly reduce, even suppress, the thrust by the bypass flow and to generate a counter-thrust by delivering an upstream-deflected flow component.
Because the door dimensions are constrained by the aerodynamic dimensions of the flow passage cleared by the outer structure 4 and by the door positioning in the thrust-reversal mode, the stationary structure has a projecting shape 12 at the outer downstream side of the fore frame 8. A more or less pronounced stagnant fluid zone 11 is typically present in all conventional door designs in this vicinity which reduces the forward airflow during thrust reversal. This stagnant zone 11 thus forms an aerodynamic plug reducing the effective cross-section of the reversal.
French patent application 2,764,339 proposes a movable fairing design, which covers the fore frame in the forward-thrust mode and rotationally retracts about a pivot linked to the stationary structure to clear a space, and an aerodynamic configuration downstream of the fore frame, which improves aerodynamic performance during thrust-reversal.
The length of the cross-section of the door exhaust 15 of the above described thrust reverser is mainly a function of door opening angle. In the forward thrust mode, the upstream edge of the stationary fairing 16 must not interfere with the flow 13 moving toward the outside through the conduit 10 of the door 3. This parameter determines the extreme upstream position the edge may assume. In the forward-thrust position, the upstream edge of the stationary fairing 16 interfaces with the downstream edge of the outer structure 4 of the door 3. Therefore, the cross-section in this design will be fixed.
French and European patent applications 2,764,339 and 0,822,327 involve solutions to increasing the length of the door exhaust's cross-sectional length by combining hinge means independent of the stationary structure.
In some thrust-reverser configurations, optimal aerodynamic performance may require simultaneously clearing the downstream frame portion and increasing the door's outlet cross-section. In such a case the techniques might be combined. If so, however, a large number of movable parts will be needed, entailing cost and weight increases and moreover at the risk of mutual interference.
Simultaneously using several techniques may substantially reduce the overall thrust-reverser reliability.